Plywood manufacture with controlled glue spread

ABSTRACT

PLYWOOD IS MANUFACTURED BY SPREADING WITH GLUE THE SURFACES OF A SEQUENCE OF WOOD VENEERS, THE SPREAD VENEERS ARE ASSEMBLED IN PLYWOOD-FORMING ASSEMBLIES. THE ASSEMBLIES ARE STACKED SEQUENTIALLY AS THEY ARE FORMED. DURING THE SPREADING OPERATION THE AMOUNT OF GLUE SPREAD IS ALTERED PROGRESSIVELY TO APPLY TO THE SUCCESSIVE VENEERS THE OPTIMUM SPREAD DETERMINED BY THEIR ASSEMBLY TIME. THE RESULTING STACK THEN IS PRESSED TO CONSOLIDATE THE ASSEMBLIES AND BOND TOGETHER THEIR COMPONENT VENEERS.

June l, 19.71 J. M. STEINBERG 3,582,428

' l I PLYWOOD MANUFACTURE WITH CNTROLLED GLUE SPREAD Fi1e1Apri1 17, 1969M Julius Mfeinberg /20 BY INVENTOR Il@ n -lilnted States Patent O1 hee3,582,428 Patented June l, 1971 3,582,428 PLYWOOD MANUFACTURE WITHCONTROLLED GLUE SPREAD Julius M. Steinberg, Hillsboro, Oreg., asslgnorto Pacific Adhesives Company, Inc. Filed Apr. 17, 1969, Ser. No. 817,092

Int. Cl. Bc 11/10; B32b 31/12 o U.S. Cl. 156-288 13 Claims ABSTRACT 0FTHE DISCLOSURE Plywood is manufactured by spreading with glue thesurfaces of a sequence of wood veneers. The spread veneers are assembledin plywood-forming assemblies. The assemblies are stacked sequentiallyas they are formed. During the spreading operation the amount of gluespread is altered progressively to apply to the successive veneers theoptimum spread as determined by their assembly time. The resulting stackthen is pressed to consolidate the assemblies and bond together theircomponent veneers.

This invention relates to the manufacture of plywood.

In the manufacture of plywood, wood veneers conventionally are spreadwith selected glues in selected types of glue spreaders. The spreadveneers are assembled in plywood-forming assemblies which are stackedsequentially as they are formed. When a stack containing the desirednumber of assemblies has` been obtained, the stack asa unit isintroduced into the press. There it is consolidated under conditionscalculated to consolidate the veneers and bond them together intoplywood.

A problem of long standing and of considerable consequence is thatoccasioned by the length of time the assemblies must remain in the stackpreliminary to pressing, i.e. the assembly time. In practice, this timevaries from about 2 to 25 minutes.

During the assembly time, the applied `glue tends to lose its solventinto the veneers to an extent which is directly proportional to thetime. As a result, there is dry out of the glue at the bottom of thestack, where long assembly times pre-vail, and over application of theglue at the top of the stack, resulting in over penetration, where shortassembly times prevail. Both of these conditions affect adversely thequality of the plywood bond.

In recognition of this problem, it currently is conventional practice inthe plywood industry to apply an amount of glue which is an averageamount. This in effect makes the best of a bad situation by over andunderspreading the veneers as little as possible.

For example, when spreading 1/10 inch core veneer in protein hotpressing, the common spread is 80 pounds per thousand square feet. Thisis an average value, since in actuality the bonding of the long assemblytime veneers would be improved if the glue spread were increased bypounds. Conversely, the bonding of the short assembly time veneers wouldbe improved if a spread of from 10-20 pounds less glue were employed.

It is the general purpose of the present invention to provide method andapparatus for overcoming the foregoing problem and to apply to asuccession of plywood veneers, to be assembled and stacked inplywood-forming relation, the optimum quantity of glue as determined bythe assembly time.

It is another important purpose of the present invention to providemethod and apparatus for achieving the before mentioned general purposesimply and without costly and complicated alteration of conventionalplywood making apparatus or plant routines.

It is a further purpose of the present invention to provide method andapparatus for achieving the above mentioned general purpose irrespectiveof whether the glue is spread on the veneers by roll coating, spraycoating, extrusion, or curtain coating methods.

In the drawings:

FIG. l is a fragmentary schematic view in side elevation illustratingplywood veneer roll coating apparatus in which the presently describedimprovement is incorporated in a first embodiment;

FIG. 2 is a fragmentary sectional view, taken along line 2-2 of -F-IG.l; and

FIGS. 3 and 4 are schematic views illustrating plywood veneer spraycoating and curtain coating apparatus, respectively, both incorporatingthe herein described irnprovement in second and third embodiments.

FIG. l illustrates the application of the invention to a plywoodmanufacturing system including a wood veneer roll coater indicatedgenerally at 10 with associated stacking table, indicated generally at12.

It is usual practice to feed wood veneers 14 through the roll coater andto assemble the resulting glue-coated core `veneers with an appropriatedisposition of face veneers to form a stack 16 of plywood-formingassemblies on table 12. For the convenience of the operator, the tableis of such a construction that it indexes downwardly as the stack isbuilt up. This keeps the upper surface of the stack at a convenientworking level.

The essential components of roll coater 10 comprise a frame 18 whichsupports a pair of cooperating gluespreading rolls 20 having shafts 22mounted in bearings 24. The bearings are mounted in a suitable verticalguideway, not illustrated, so that the rolls may be moved toward andaway from each other by means of pneumatic cylinders 26. The latter maybe spring-pressed or double acting and are supplied with air underpressure by means of a pneumatic line 28. Line 28 includes an airregulating valve 30.

Rolls 20 serve the dual functions of applying glue to the veneers and ofconveying the veneers through the unit. They are driven by aconventional drive, not illustrated.

Also included in the roll spreader are a pair of doctor rolls 32. Thesehave for their function loading spreader rolls 20 with glue 33. They aremounted on shafts 34 supported on bearings 36 which are received inguideways 38. Screws 40 are attached to the bearings for adjusting them,and doctor rolls 32, which they support, inwardly and outwardly withrespect to applicator rolls 20.

lIt is the present concept to vary the amount of glue applied tosuccessive veneers as they pass through the apparatus in a mannerresulting in the application of the optimum amount of glue to eachveneer as required to insure optimum bonding after the panels have beenassembled, stacked, and pressed.

This may be accomplished by appliances which Work on a unit basis, i.e.adjust glue spreads progressively with the number of units put throughthe spreader, or on a time basls, i.e. adjust spreads progressively withthe time required to coat and assemble the veneers comprising stack 16.This time is substantially a constant factor.

b 'Ihhe arrangement illustrated in FIG. l utilizes the unit asis.

Stacking table 12 is provided with a bracket 44 to which is attached oneend of a cable or other eXible link 46. The cable is reeved about apulley 48. The other end of the cable is fastened to a rotatable drum 50suitably biased by means of a spring 52.

Drum 50 is fixed to the input shaft 54 of an electrically operated servomotor 56. The latter may be any one of various standard makes all ofwhich serve the general function of modifying a command power input,i.e. that fed into the mechanism by input shaft 54, as required toproduce a predetermined power output on an associated output shaft 58.

If desired, a conventional electrical impulse generator, notillustrated, may be mounted on the shaft of pulley 48 and connected tothe servo motor, replacing drum assembly 50.

Power output shaft 58 carries three sprockets. The rst drives aconnecting chain 60 which meshes with a sprocket t62. This adjusts airvalve 30 and controls the air supply to cylinders 2-'6 which adjust thespacing of glue applicator rolls 20.

The other two sprockets on power shaft 58 drive chains 64. These meshwith sprockets 68 fixed to screws 40. The latter are arranged in pairs,two on each side of doctor rolls 32, the sitting of which they adjust.The members of each pair of screws are interconnected by I chains 70.

The operation of the apparatus of FIGS. 1 and 2 is as follows:

As the stack of plywood assemblies 16 on table 12 is built up, table 12is indexed downwardly to keep the top of the stack at substantiallyconstant level. At the beginning of the operation, flexible cable 46 iswound about spring-biased drum 50 on shaft 52. However, with lowering oftable 12, cable 46 unwinds and rotates shaft 52. This in turn energizesservo motor 56 and drives power shaft 58. This has two effects, eitherone of which may be used to achieve the desired result.

First, it drives chain 60 and sprocket y62 on valve 30, adjusting thevalve by progressively opening or closing it. In the usual situationvalve 30 operates to apply greater air pressure to cylinders 26 with theresult that spreader rolls associated with the cylinders are adjusted topositions in which they continually more closely approach each other.This has the effect of decreasing the spread of glue applied to veneers14.

Secondly, shaft S8 drives chains 64 which in turn drive all of screws40. `In the usual case, these work to advance doctor rolls 32 with whichthey are associated so that they more closely approach spreader rolls 20and decrease the amount of glue applied to the veneers.

There thus is obtained a progressive adjustment of the spreader rollsand doctor rolls to decrease the amount of glue applied to the veneersas stack 16 increases in height. As a result, increased amounts of glueare applied to the lowermost assemblies of the stack, which have thelongest assembly time; progressively decreased amounts, to besuperimposed assemblies. The least amount of glue then is applied t theupper assemblies which have the shortest assembly time. In this mannerthe optimum amount of glue may be applied to all `of the assemblies.

The operation of the unit illustrated in FIG. 3 is similar, except thatit illustrates application of the system to a spray coatingapparatus,and utilizes a time control rather than a unit control.

As illustrated schematically in FIG. 3, a conveyor 74 conveys plywoodveneers 76 past a spray station in which they are sprayed with glue bymeans of appropriately constructed and disposed spray heads 78. Thespray heads may be of either the airless or air categories and aresupplied with glue under pressure through lines 80. A pump 82 is drivenby a motor 84. It pumps glue from a reservoir 86 through conduit 80 andthrough a 'valve 88 to deliver it in controlled amount of spray heads 78. Valve 88 is regulated by means of a shaft on which is mounted asprocket 90.

The latter sprocket and the valve which it operates are controlled bymeans of a timer or panel counter 92. The indicator 94 of the timer isconnected by means of a exible cable 96 to a drum 98.

Drum 98 of FIG. 3 corresponds in its operation to drum 50 of FIG. 1. Itis fixed to a shaft 1100 and biased to a wound-up position by means ofspring 103.

Shaft 100 supplies the input power to a servomechanism 102 having apower shaft 104. The latter mounts a sprocket 106 which meshes with adrive chain 108. The

chain in turn meshes with sprocket which regulates valuve 88.

Since on a given plant schedule the time is known which is required tobuild up the stack of plywood assemblies comprising the predeterminedpress load, timer 92 can be set accordingly. Thus ts the spray unitoperates, lever 94 of the timer moves clockwise, unwinding drum 98against the force of spring 103. This rotates servo motor power inputshaft which adjust valve 88 through the action of output shaft 104 andconnecting chain 108.

Normally the adjusting is made in the direction of continuouslydecreasing the quantity of glue fed to spray heads 78. Since conveyor 74moves at a constant rate, this has the effect of continuouslydiminishing the spread of glue applied to veneers 76 as time progresses.

As a consequence, the lower assemblies of the press load have an optimumheavy coat of glue while the uppermost assemblies, having the shortestassembly time, have a correspondingly lesser amount of glue as requiredto produce optimum bond in all of the component assemblies of the pressload.

The apparatus illustrated in FIG. 4 illustrates the application of theherein described principle to the operation of a plywood veneer pressurefeed or gravity feed curtain coater controlled by an actuator working onthe unit principle, as is the case with the apparatus of FIG. l,depicting the pressure feed type.

A conveyor 110 conveys plywood veneers 112 past a. coating station whichincludes a curtain coater 114 of standard construction.

The curtain coater is supplied with glue from a reservoir 116. The glueis pumped by means of a vari-drive motor 118 which, in turn, drives pump120. The varidrive motor and pump unit thus serve a valving function,since the amount of glue circulated through the system is directlyproportional to the speed of the motor.

Glue then is pumped through conduit 122 into curtain coater 114. Surplusglue is collected in funnel 124 which return it to reservoir 116 throughpipes 126.

This much of the curtain coater assembly is standard.

As the veneers are coated, they are laid up into plywood-formingassemblies on stacking table which corresponds to table 12 in FIG. l. Asa stack 132 of plywood assemblies is built up on the work table, thelatter is indexed downwardly to keep the work surface level. Thismovement drives the mechanism which controls the rate of application ofthe glue to the veneers.

Work table 130 mounts a laterally extending bracket 134 to which isconnected through a pin and clevis 136 the piston rod of a double-actinghydraulic cylinder 138.

Cylinder 138 communicates through hydraulic conduits 140 with an oilreservoir 142 and with a cooperating double-acting cylinder 144. Thepiston rod of the latter cylinder is coupled to the control lever 146 ofvari-drive motor 118.

Thus, as work table 130 lowers, cylinder 138 forces oil into cylinder144, the piston rod of which adjusts lever 146 commensurately. This inturn adjust vari-drive motor 118 and controls the amount of glue pumpedby pump 120 to curtain coater 114.

Hence in this case also, the amount of glue applied to the veneers maybe altered progressively. Normally, as stack 132 builds up on table 130,the result is progressively to diminish the amount of glue supplied tocurtain coater 114 and hence applied to wood veneers 112. In this mannerthe desired control of the amount of glue applied to the veneers isachieved.

Having thus described my invention in preferred em bodiments, I claim asnew and desire to protect by Letters Patent:

1. The method of making plywood which comprises:

(a) spreading with glue selected surfaces of a sequence of wood veneers,

(b) assembling the veneers in plywood-forming assemblies,

(c) stacking the assemblies sequentially as they are formed,

(d) adjusting the amount of glue spread on the veneers progressively toalter the amount of glue applied to successive veneers and therebyprovide optimum glue spreads for all assemblies as determined by theirassembly times, and

(e) pressing the stack to consolidate the assemblies and bond togethertheir component veneers.

2. The method of claim 1 wherein the amount of glue spread on theveneers progressively is diminished.

3. For use in the manufacture of plywood, the combination of (a) gluespreader means,

(b) conveyor means for conveying a sequence of wood veneers through theglue spreader means while spreading their surfaces with glue,

(c) stacking means for stacking the spread veneers in plywood-formingassemblies preliminary to pressing the stack as a unit; and

(d) control means operatively connected to the spreader means foraltering the amount of glue applied to the veneers progressively withthe time of assembling the veneers, as required to provide optimum gluespreads for the veneers as determined by their assembly times.

4. The combination of claim 3 wherein the glue spreader means comprisesroll-type glue spreader means.

5. The combination of claim 3 wherein the glue spreader means comprisesroll-type glue spreader means including a pair of cooperating gluespreader rolls and adjusting means for adjusting the spacing between therolls, and wherein the control means is operatively connected to theadjusting means.

=6. The combination of claim 5 wherein the control means comprisestiming means operatively connected to the adjusting means.

7. The combination of claim 5 wherein the stacking means comprises avertically indexable stacking table and wherein the control meanscomprises motor means connected to the adjusting means and link meansinterconnecting the motor means and the stacking table and operative totranslate motion of the stacking table into energization of the motormeans commensurately with the movement of the table.

8. The combination of claim 3 wherein the glue spreader means comprisesroll spreader means including a spreader roll and associated doctor rollwith adjusting means for adjusting the position of the doctor rolltoward and away from the spreader roll and wherein the control meansoperatively is connected to the adjusting means.

-9. The combination of claim 3 wherein the glue spreader means comprisesglue spray means including a uid circuit for circulating glue underpressure to the spray means, and including valve means in the circuitoperative to control the amount of glue fed to the spray means, thecontrol means being operatively connected to the valve means foraltering the amount of glue applied to the veneers progressively withthe time of assembly.

10. The combination of claim 3 wherein the glue spreader means comprisescurtain coating means including a circuit for circulating glue underpressure to the curtain coater means, the circuit including valve meansfor controlling the flow of glue through the circuit, and wherein thecontrol means operatively is connected to the valve means for alteringthe amount of glue supplied to the veneers progressively with theassembly time.

11. The combination of claim 3 wherein the stacking means comprises avertically adjustable stacking table provided with drive means foradjusting its elevation progressively as the stack increases in heightand wherein the control means comprises servo motor means having inputand output shafts, rst connecting means interconnecting the input shaftand the table, and second connecting means interconnecting the outputshaft and the glue spreader means.

12. The combination of claim 3 wherein the stacking means comprises avertically indexable stacking table incrementally shiftable as the workstack builds up upon it, the control means comprising a pair ofhydraulic cylinders in hydraulic circuit with each other in seriesrelationship, one cylinder being operatively connected to the table andthe other cylinder being operatively connected to the glue spreadermeans for altering the amount of glue applied to the veneersprogressively with the assembly time and in amount determined by theadjustment of the irst cylinder by movement of the stacking table.

13. The combination of claim 3 wherein the control means comprises servomotor means having input output shafts, timer means connected to theinput shaft for actuating the same, and connecting means interconnectingthe output shaft with the glue spreader means for adjusting the amountof glue applied to the veneers commensurately with the lapsed time asdetermined bythe time means.

References Cited UNITED STATES PATENTS 2,822,024 2/ 1958 Himmelheber156-360 3,037,900 6/ 1962 Hings et al 156-314X 3,085,582 4/ 1963 Slosmanet al. 11S-8X 3,137,601 6/1964 Menzer 156--550X 3,367,823 2/ 1968Clausen et al 156-559X 3,384,524 5/ 1968 Hansen 156-360 BENJAMIN A.BORCHELT, Primary Examiner I M. HANLEY, Assistant Examiner U.S. C1. X.R.

